He said the measure "marks important progress in the protection of America's children."

"When a child is reported missing, that case becomes a matter of the most intense and focused effort by law enforcement," Bush said as Elizabeth Smart and families of other kidnapped children looked on in the White House Rose Garden. "Entire communities join in the search and, through unrelenting efforts, many children have been saved."

The measure, dubbed the "Protect Act of 2003," also enhances penalties for youth abductions and child sex crimes, boosts funding for missing and exploited children programs and cracks down on child pornography, including images created digitally.

Amber Alerts use radio, television, roadside electronic billboards and emergency broadcast systems to disseminate information about kidnapping suspects and victims soon after the abduction of a child under 18 is reported. In such cases, authorities say, the child could be killed or seriously injured a short time after being kidnapped.

The alerts -- named after a 9-year-old Texas girl, Amber Hagerman, who was kidnapped and killed in 1996 -- are currently in effect in 41 states. Bush said they "have become an increasingly important tool in rescuing kidnapped children."

"Every person who would think of abducting a child can know that a wide net will be cast," he said. "They may be found by a police cruiser or by the car right next to them on a highway. These criminals can know that any driver they pass could be the one that spots them and brings them to justice."

Amber's mother, Donna Norris, attended the ceremony along with the survivors of two high-profile kidnapping cases -- Jacqueline Marris and Tamara Brooks, two California teenagers rescued in the first use of the system in that state; and Utah teen Elizabeth Smart, whose father, Ed Smart, called for a national Amber alert system after her recovery in March.

He initially assailed lawmakers -- specifically Rep. James Sensenbrenner, R-Wisconsin, chairman of the House Judiciary Committee -- for wanting to include the Amber Alert measure as part of a broader child protection bill. But Bush singled out Sensenbrenner for praise Wednesday, saluting his "fine work."

The new law encourages states to develop Amber Alert systems. Attorney General John Ashcroft said the bill aims to create a "seamless" system across the country.

The Bush administration has designated an Amber Alert coordinator at the Justice Department to assist states and has designated $10 million for that effort.

"It's very important, because in most cases where children are seriously hurt or killed, they are killed during the early hours of the abduction," Ashcroft told CNN. "And so we want to have the alert not only be a substantial and broad alert, but it has to happen early and quickly. That's why it's important we have this additional funding and this coordination at the national level."